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Abstract

It is widely understood among scientists and criminal and civil lawyers that eyewitnesses are often inaccurate, and that inaccurate information can contaminate memories of other eyewitnesses. It is less widely known—although no less true—that when misleading claims are repeated, they are more likely to damage other people’s memories than when those claims are made only once. But until recently, neither lawyers nor scientists knew the answer to these questions: Does one person repeating an inaccurate claim do more damage to the memories of other eyewitnesses than that same person making the claim only once? And when that inaccurate claim is repeated, does it matter how many people make it? In this paper, we address those questions.

Suppose a robbery occurs for which there were four eyewitnesses. If one eyewitness, let’s call him John, mistakenly tells another eyewitness, Ringo, that the robber was wearing a blue hat—when in fact the robber was wearing a black hat—than we know Ringo may, inadvertently, remember later that the robber was wearing a blue hat. But would Ringo be even more likely to make this mistake if John had repeated that inaccurate claim multiple times? By contrast, suppose that all of the eyewitnesses— John, Paul, and George—mistakenly claimed it was a blue hat. Would their converging evidence be more misleading to Ringo than if John had simply repeated it multiple times? Put another way, do inaccurate claims do more damage when made by multiple sources, or is it the repetition of claims that matters?